DESCRIPTION: In this renewal application, the applicant proposes to continue efforts to unravel the mechanisms by which viral transactivators and the cellular transcription apparatus interact with each other to regulate gene expression. In particular, a significant effort will be devoted to isolating, cloning and characterizing members of a novel class of transcription factors called TAFs/coactivators which are responsible for mediating regulation by enhancer binding proteins. The applicant hopes to develop in vitro and in vivo assays to dissect the function of independent TAFs as well as the TBP/TAF complex. One intriguing and important objective is to search for putative cell-type specific TAFs. A significant effort will also be directed at interactions between the viral oncogene, T antigen, tumor suppressors (p53) and components of the transcription machinery. A major new area of investigation will be the development of reconstituted transcription reactions designed to evaluate the individual steps along the transcription cycle that may be subject to regulation by specific viral and cellular factors. Finally, the applicant hopes to begin high resolution structural analysis of various protein:protein interfaces that form the basis of activator:coactivator interactions. In particular, he will employ a battery of biochemical and physical methods to determine the 3D structure of activation domains and to test various hypotheses concerning the dynamic process of transcription factor interplay.